Light source, method of manufacturing the light source, and method of mounting the light source

ABSTRACT

A light source includes a light emitting element configured to emit a light; a mounting substrate; and a ceramic substrate having a light emitting element mounted thereon and being bonded to the mounting substrate via a plurality of metal bumps made of gold, copper, a gold alloy, or a copper alloy. A method of manufacturing a light source includes forming a plurality of metal bumps on a mounting substrate; providing a ceramic substrate having at least one light emitting element mounted thereon; and bonding the mounting substrate and a ceramic substrate to each other via the metal bumps.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/869,499, filed on Sep. 29, 2015, which claims priority to JapanesePatent Application No. 2014-199677, filed on Sep. 30, 2014, the contentsof which are hereby incorporated by reference in their entireties.

BACKGROUND

Technical Field

The present disclosure relates to a light source, a method ofmanufacturing the light source, and a method of mounting the lightsource.

Description of Related Art

There are known semiconductor devices in which a supporting substrate isdisposed on a mounting substrate (for example, see JP 2001-210746 A andJP 2004-259798 A).

JP 2001-210746 A discloses a ceramics multilayer wiring substrate towhich bump conductors are bonded. As the bump conductors, solder ballsare used.

JP 2004-259798 A discloses that, a semiconductor chip, a first chipsupporting substrate supporting the semiconductor chip, a second chipsupporting substrate on which the first chip supporting substrate isformed are disposed on a mounting substrate. Bump electrodes are formedat the second chip supporting substrate. The second chip supportingsubstrate is connected to the mounting substrate via the bump electrode.As the bump electrodes, solder balls are used.

However, the bumps made of solder balls cannot provide sufficientbonding strength between the ceramics multilayer wiring substrate andthe mounting substrate.

SUMMARY

Accordingly, an object of certain embodiments of the present inventionis to provide a light source exhibiting high bonding strength between aceramic substrate and a mounting substrate, and a method ofmanufacturing the same.

A light source according to certain embodiments includes a lightemitting element adapted to emit a light, a mounting substrate and aceramic substrate. The light emitting element is mounted on the ceramicsubstrate, and the ceramic substrate is bonded to the mounting substratevia a plurality of metal bumps made of gold, copper, a gold alloy, or acopper alloy.

A method of manufacturing a light source according to certainembodiments includes forming a plurality of metal bumps on the mountingsubstrate, bonding the mounting substrate and a ceramic substrate havinga light emitting element mounted thereon and being placed on themounting substrate, to each other via the metal bumps.

A method of mounting according to certain embodiments includes forming aplurality of metal bumps on a mounting substrate, and bonding themounting substrate and a ceramic substrate placed on the mountingsubstrate, to each other via the metal bumps.

According to the arrangement described above, a light source having highbonding strength between a ceramic substrate and a mounting substrate,and a method of manufacturing the same can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view showing a light source accordingto a first embodiment.

FIG. 2 is a schematic cross-sectional view, taken along line II-II inFIG. 1, showing the light source according to the first embodiment.

FIG. 3 is a schematic cross-sectional view showing a step ofmanufacturing the light source according to the first embodiment.

FIG. 4 is a schematic cross-sectional view showing a step ofmanufacturing the light source according to the first embodiment.

FIG. 5 is a schematic cross-sectional view showing a step ofmanufacturing the light source according to the first embodiment.

FIG. 6 is a schematic cross-sectional view showing a step ofmanufacturing the light source according to the first embodiment.

FIG. 7 is a schematic cross-sectional view showing a step ofmanufacturing a light source according to a second embodiment.

FIG. 8 is a schematic cross-sectional view showing a step ofmanufacturing a light source according to a third and a fourthembodiments.

FIG. 9 is a schematic plan view showing a light source according toExample 1.

FIG. 10 is a schematic cross-sectional view, taken along line X-X inFIG. 9, showing the light source according to Example 1.

FIG. 11 is a schematic side view showing the light source according toExample 1.

FIG. 12 is a schematic side view showing the light source according toExample 1.

FIG. 13 is a schematic back view showing the light source according toExample 1.

DETAILED DESCRIPTION

In the following, a light source and a method of manufacturing the same,according to embodiments of the present invention will be described.Note that the present invention is not limited to the embodiments andexamples.

For the sake of convenience, the side of a mounting substrate on whichlight-emitting elements are disposed is referred to as the upper surfaceside or the plan side.

First Representative Embodiment

A light source according to a first embodiment will be described belowwith reference to the drawings. FIG. 1 is a schematic perspective viewshowing the light source according to the first embodiment. FIG. 2 is aschematic cross-sectional view, taken along line II-II in FIG. 1,showing the light source according to the first embodiment.

The light source includes a mounting substrate 10, metal bumps 20, aceramic substrate 30, light-emitting elements 40, and a sealing member50.

The mounting substrate 10 is an approximately rectangular parallelepipedmember formed in a cup-shape having a bottom surface and side surfaces,and defining an opening. In a plan view, a periphery defining theopening of the cup-shaped portion has a quadrangular shape with roundedcorners. The mounting substrate 10 can be formed with a copper materialand a thermoplastic resin. For the thermoplastic resin, apolyphthalamide, a liquid crystal polymer, a polybutylene terephthalate(PBT), an unsaturated polyester or the like may be used. Alternatively,the mounting substrate 10 can be made of a copper material and ceramics.The mounting substrate 10 may have a planar shape. The mountingsubstrate 10 may be made solely of copper or a copper alloy. Also, aglass epoxy substrate, an epoxy substrate, or a metal substrate may beused as the mounting substrate 10. Electrical connection of the mountingsubstrate 10 with an external electrode can be established through ametal member disposed only on a predetermined portion while aninsulating material is disposed on other portions.

On the ceramic substrate 30, the light-emitting elements 40 are mounted.The light-emitting elements 40 may be mounted either in a face up manneror in a face down manner. The light-emitting elements 40 are preferablynitride semiconductors, but other semiconductors can also be used.

The ceramic substrate 30 can be made of an electrically insulatingmaterial. Examples thereof include an alumina-based sintered body suchas alumina (Al₂O₃), a mullite (3Al₂O₃.2SiO₂)-based sintered body, asilicon carbide (SiC)-based sintered body, a glass ceramics-basedsintered body, an aluminum nitride (AlN). The ceramic substrate 30 isprovided with a single-layer wiring or a multilayer wiring. The ceramicsubstrate 30 provided with the single-layer wiring or the multilayerwiring can be formed as follows. A metal paste is obtained by adding anappropriate organic resin binder, a plasticizer, and a solvent to powderof a high melting point metal such as tungsten, molybdenum, manganese orthe like, and mixing them. The metal paste is applied on a ceramicsgreen sheet in a predetermined pattern by using a print coating method.Then, the green sheet is calcined.

The ceramic substrate 30 on which the light-emitting elements 40 aremounted is bonded to the mounting substrate 10 using a plurality ofmetal bumps 20 made of gold, copper, a gold alloy or a copper alloy.Gold is preferable but a gold alloy whose main component is gold mayalso be used. In the case of using gold as the main component, 75% byweight or more of gold is contained, in which 80% by weight or more ispreferable and 90% by weight or more is most preferable. From theviewpoint of reflectivity, ductility, and malleability, gold ispreferable. However, copper or a copper alloy can also be used. Aplurality of metal bumps 20 are used. The metal bumps 20 can be formedon the entire mounting surface of the ceramic substrate 30, but themetal bumps 20 can also be formed densely at a location where cracks areprone to occur. For example, the metal bumps 20 may be densely arrangedin the vicinity of the center of the ceramic substrate 30, and may besparsely arranged in the vicinity of outer periphery of the ceramicsubstrate 30. In the case where the ceramic substrate 30 has a shapelong in one direction, cracks are prone to occur in the directionperpendicular to the length direction. Accordingly, a plurality ofcolumns of metal bumps 20 may be formed in the length direction in thevicinity of the center of the length direction.

The light-emitting elements 40 and the ceramic substrate 30 are coveredby the sealing member 50. For the sealing member 50, a thermosettingresin such as an epoxy resin, a silicone resin, or the like can be used,and other than those resins, glass may also be used.

In a plan view, a resin 60 is filled between a plurality of metal bumps20, so as to improve the bonding strength between the ceramic substrate30 and the mounting substrate 10. The resin 60 may contain particleshaving high thermal conductivity, such as silver, copper, aluminum andthe like. With the arrangement described above, heat accumulated in theceramic substrate 30 can be efficiently transferred to the mountingsubstrate 10 side.

In the case of bonding the ceramic substrate 30 and the mountingsubstrate 10 made of a copper material, due to difference in the thermalhysteresis during solder mounting, arising from a large difference incoefficients of thermal expansion therebetween, a great thermal stressmay be loaded on the ceramic substrate, resulting in occurrence ofcracks. Solder mounting requires a reflow step, and it is consideredthat cracks attributed to the difference in coefficients of thermalexpansion between the ceramic board 30 and the mounting substrate 10occur in the reflow step. In order to prevent occurrence of cracks inthe ceramic substrate 30, bonding with the use of an epoxy resin may beconsidered, with the aim of reducing the stress. However, as compared tobonding using solder, the bonding property and the heat releasingproperty are largely reduced. Hence, the use of an epoxy resin has beendisadvantageous. Accordingly, as the light source according to the firstembodiment, bonding the ceramic substrate 30 having the light emittingelements 40 mounted thereon and the mounting substrate 10 by using aplurality of metal bumps 20 made of gold, copper, a gold alloy, or acopper alloy allows for production of a light source in which thebonding strength between the ceramic substrate 30 and the mountingsubstrate 10 is enhanced and good heat releasing property can beobtained. Further, since the metal bumps 20 are used, gaps are createdbetween the ceramic substrate 30 and the mounting substrate 10 in across-sectional view. Due to the gaps or the like, reduction in thethermal stress between the ceramic substrate 30 and the mountingsubstrate 10 and reduction in the occurrence of cracks in the ceramicsubstrate 30 can be achieved. By filling the gaps with the resin 60, thebonding strength can further be improved, and also the heat releasingeffect can be improved.

A method of manufacturing the light source according to the firstembodiment will be described with reference to the drawings. FIGS. 3 to6 are schematic cross-sectional views illustrating the steps ofmanufacturing the light source according to the first embodiment.

A plurality of metal bumps 20 are formed on the mounting substrate 10.

A plurality of metal bumps 20 are formed on a surface of the mountingsubstrate 10 that serves as an inner bottom surface of a cup-shapedportion. For example, the metal bumps 20 may each have a diameter ofabout 60 μm to about 120 μm, and a height of about 20 μm to about 50 μm.The metal bumps 20 are arranged in the longitudinal and lateraldirections. Metal bumps 20 made of gold are typically used, but metalbumps made of copper, a gold alloy, or a copper alloy can also be used.A purity of gold of 95% or more is preferable, and 99% or more is morepreferable.

On the mounting substrate 10, the ceramic substrate 30 on which thelight-emitting elements 40 are mounted is placed, and the mountingsubstrate 10 and the ceramic substrate 30 are bonded to each other viathe metal bumps 20.

The ceramic substrate 30 has an approximately quadrangular shape in aplan view. On the ceramic substrate 30, the light-emitting elements 40are arranged in a matrix of three rows and three columns. The number ofthe light-emitting elements 40 can be changed as appropriate. Thelight-emitting elements 40 are mounted in a face down manner on theceramic substrate 30.

Bonding between the mounting substrate 10 and the ceramic substrate 30can be performed at a temperature of 100° C. to 200° C., while applyinga pressure of 1.0 kg/mm² to 5.0 kg/mm².

Next, the resin 60 is poured into the gap between the mounting substrate10 and ceramic substrate 30. An epoxy resin is used as the resin 60, anda silver filler is contained in the epoxy resin.

The viscosity of the epoxy resin is adjusted as appropriate in view ofwettability or the like of the mounting substrate 10 and the ceramicsubstrate 30. For example, the epoxy resin with a discharge pressure of150 kPa to 400 kPa is preferably employed. A silver filler having aparticle size of about 0.1 μm to about 10 μm can be used.

Next, using the sealing member 50, the light-emitting elements 40 on theceramic substrate 30 are covered. The sealing member 50 is applied bypotting. In place of potting, any appropriate application method such asspraying, compression molding, extrusion molding, injection molding,transfer molding or the like may be used. The sealing member 50 may bemade of an epoxy resin, a silicone resin or the like. The sealing member50 is cured.

Thus, the light source according to the first embodiment can be easilymanufactured.

In the first embodiment, the resin 60 is used, but the light emittingelements 40 may be covered with the sealing member 50 after bonding theceramic substrate 30, without the use of the resin 60.

Second Representative Embodiment

In place of the method of manufacturing a light source according to thefirst embodiment, the light source according to the first embodiment canbe manufactured by a method of manufacturing a light source according toa second embodiment. FIG. 7 is a schematic cross-sectional view showingthe process of manufacturing a light source according to the secondembodiment.

First, a plurality of metal bumps 20 are formed on the mountingsubstrate 10.

Next, the ceramic substrate 30 is placed on the mounting substrate 10,and the mounting substrate 10 and the ceramic substrate 30 are bonded toeach other via the metal bumps 20.

Next, the light-emitting elements 40 are mounted on the ceramicsubstrate 30.

Next, the resin 60 is poured into the gap between the mounting substrate10 and the ceramic substrate 30.

Next, the light-emitting elements 40 on the ceramic substrate 30 arecovered with the sealing member 50.

The light-emitting elements 40 are mounted on the ceramic substrate 30after the mounting substrate 10 and the ceramic substrate 30 are bondedto each other, so that the heat at the time of bonding the mountingsubstrate 10 and the ceramic substrate 30 does not influence thelight-emitting elements 40. Hence, thermal damage to the light-emittingelements 40 can be reduced.

Third Representative Embodiment

In place of the method of manufacturing a light source according to thefirst embodiment, the light source according to the first embodiment canbe manufactured by a method of manufacturing a light source according toa third embodiment. FIG. 8 is a schematic cross-sectional view showingthe process of manufacturing a light source according to the thirdembodiment.

A plurality of metal bumps 20 made of gold, copper, a gold alloy or acopper alloy are formed on the ceramic substrate 30. The metal bumps 20are formed on the back surface side of the ceramic substrate 30.

The ceramic substrate 30 is placed on the mounting substrate 10, and themounting substrate 10 and the ceramic substrate 30 are bonded to eachother via the metal bumps 20.

The light-emitting elements 40 are mounted on the ceramic substrate 30.

The metal bumps 20 are formed on the ceramic substrate 30 side, so thatthe alignment control between the ceramic substrate 30 and the mountingsubstrate 10 can be eliminated. In the case where the cup-like mountingsubstrate 10 is used, the metal bumps 20 may be difficult to be formedin the cup. In such a case, with the use of a planar ceramic substrate30, the metal bumps 20 can be easily formed.

The light-emitting elements 40 are mounted on the ceramic substrate 30after the mounting substrate 10 and the ceramic substrate 30 are bondedto each other, so that the heat at the time of bonding the mountingsubstrate 10 and the ceramic substrate 30 does not influence thelight-emitting elements 40. Hence, thermal damage to the light-emittingelements 40 can be reduced.

Fourth Representative Embodiment

In place of the method of manufacturing a light source according to thefirst embodiment, the light source according to the first embodiment canbe manufactured also by a method of manufacturing a light sourceaccording to a fourth embodiment. FIG. 8 is a schematic cross-sectionalview showing the process of manufacturing a light source according tothe fourth embodiment.

A plurality of metal bumps 20 made of gold, copper, a gold alloy or acopper alloy are formed on the ceramic substrate 30 on which thelight-emitting elements 40 are mounted.

The ceramic substrate 30 is placed on the mounting substrate 10, and themounting substrate 10 and the ceramic substrate 30 are bonded to eachother via the metal bumps 20.

The metal bumps 20 are formed on the ceramic substrate 30 side, so thatthe alignment control between the ceramic substrate 30 and the mountingsubstrate 10 can be eliminated. Further, in the case where the cup-likemounting substrate 10 is used, the metal bumps 20 may be difficult to beformed in the cup. In such a case, with the use of a planar ceramicsubstrate 30, the metal bumps 20 can be easily formed.

Note that, in the methods of manufacturing a light source according tothe second to fourth embodiments, in the step of bonding the mountingsubstrate 10 and the ceramic substrate 30 to each other, the gapsbetween the metal bumps 20 may be filled with the resin 60 after thebonding with the metal bumps 20.

Further, in the methods of manufacturing a light source according to thesecond to fourth embodiments, the light-emitting elements 40 on theceramic substrate 30 is covered with the sealing member 50.

Method of Mounting

A method of mounting the mounting substrate 10 and the ceramic substrate30 will be described below.

A plurality of metal bumps 20 are formed on the mounting substrate 10.

The ceramic substrate 30 is placed on the mounting substrate 10, and themounting substrate 10 and the ceramic substrate 30 are bonded to eachother via the metal bumps 20.

Further, as another embodiment, a plurality of metal bumps 20 made ofgold or a gold alloy are formed on the ceramic substrate 30. On themounting substrate 10, the ceramic substrate 30 is placed, and themounting substrate 10 and the ceramic substrate 30 are bonded to eachother via the metal bumps 20.

The thermal hysteresis during bonding of the mounting substrate 10 andthe ceramic substrate 30 to each other can be reduced. Thus, occurrenceof cracks in the ceramic substrate 30 can be prevented.

Other Constituent Elements

It is also possible to arrange a light-transmissive substrate on thelight-emitting elements. The light-transmissive substrate may containone or more of a phosphor, a reflective member, a light-diffusing memberand the like. The light-emitting elements and the light-transmissivesubstrate may be bonded to each other using an adhesive agent. Further,it is also possible to dispose the light-emitting elements on the bottomsurface in the cup of the cup-like mounting substrate, arrange alight-transmissive substrate on the light-emitting elements, and fix theouter circumference by resin. The resin may be filled in the cup. Theresin may contain one or more of a light-reflective material, adiffusing agent, a heat conductive member, pigment, a light-absorbingagent and the like, the resin preferably contains a light-reflectivematerial. This is because, the light from the light-emitting elements isirradiated on the resin that contains the light-reflective material,then is reflected and emitted to the outside. The resin is preferably athermosetting resin such as an epoxy resin, a silicone resin, an urearesin or the like, but it is also possible to employ a thermoplasticresin such as a polyphthalamide, a liquid crystal polymer, apolybutylene terephthalate (PBT), an unsaturated polyester or the like.

The sealing member may contain one or more of a phosphor, a diffusingagent, a heat conductive member, a pigment, a light-absorbing agent andthe like. A protective element may be disposed on the ceramic substrate.The light-emitting elements can be mounted on the ceramic substrate in aface down manner by using metal bumps, or may be mounted in a face upmanner by using a resin.

EXAMPLE 1

A light source according to Example 1 will be described below withreference to drawings. FIG. 9 is a schematic plan view showing the lightsource according to Example 1. FIG. 10 is a schematic cross-sectionalview, taken along line X-X in FIG. 9, showing the light source accordingto Example 1. FIG. 11 is a schematic side view showing the light sourceaccording to Example 1. FIG. 12 is a schematic side view showing thelight source according to Example 1. FIG. 13 is a schematic back viewshowing the light source according to Example 1. The description of thestructure substantially similar to that of the light source according tothe first embodiment may be partially omitted.

The light source includes the mounting substrate 10, the metal bumps 20,the ceramic substrate 30, the light-emitting elements 40, the sealingmember 50, and the resin 60.

The mounting substrate 10 is made of a planar copper material and athermoplastic resin. For the thermoplastic resin, a polyphthalamide isused. The mounting substrate 10 has an approximately rectangularparallelepiped shape, with a longitudinal length of 2.5 mm, a laterallength of 5.1 mm, and a height of 0.75 mm. The mounting substrate 10 hasan approximately rectangular cup-like shape in a plan view, with alongitudinal length of 1.2 mm, a lateral length of 4.6 mm, and a depthof about 0.35 mm. At the back surface of the mounting substrate 10, ananode electrode and a cathode electrode each having an approximatelysquare shape with a side of about 2.1 mm are disposed respectively.

The ceramic substrate 30 has a plate-like and approximately rectangularparallelepiped shape, with a longitudinal length of 1.0 mm, a laterallength of about 4.4 mm, and a thickness of 0.2 mm. The main component ofthe ceramic substrate 30 is alumina, and the ceramic substrate 30includes predetermined internal wiring and external wiring.

On the ceramic substrate 30, the light-emitting elements 40 are mounted.The light-emitting elements 40 each has a substantially square shape,with a side of about 800 μm. Four light-emitting elements 40 are mountedin the length direction of the ceramic substrate 30.

A plurality of metal bumps 20 are formed on the mounting substrate 10.The metal bumps 20 are made of gold. The metal bumps 20 each have adiameter of 60 μm to 120 μm and a height of about 40 μm. The purity ofgold is 99.9%.

The ceramic substrate 30 on which the light-emitting elements 40 aremounted and the mounting substrate 10 are bonded to each other using themetal bumps 20.

At the gap between the mounting substrate 10 and the ceramic substrate30, the resin 60 is arranged. For the resin 60, a phenyl silicone resincontaining silver particles is used.

The sealing member 50 contains a phosphor. For the sealing member 50, adimethyl silicone resin is used, and for the phosphor, a YAG phosphor isused.

Thus, the light source having high bonding strength between the mountingsubstrate 10 and the ceramic substrate 30 can be provided.

The light source according to Example 1 can be manufactured according toa method described below.

A plurality of metal bumps 20 are formed on the mounting substrate 10.The metal bumps 20 are made of gold, and arranged in a matrix of threecolumns and twelve rows.

Next, the ceramic substrate 30 on which the light-emitting elements 40are mounted is placed on the mounting substrate 10, and the mountingsubstrate 10 and the ceramic substrate 30 are bonded to each other viathe metal bumps 20. The mounting substrate 10 and the ceramic substrate30 are bonded to each other via the metal bumps 20 under a temperatureof 100° C. to 200° C. and a pressure of 2.2 kg/mm².

Next, the resin 60 is poured into the gap between the mounting substrate10 and the ceramic substrate 30.

The resin 60 is poured at a discharge pressure of 160 kPa to 350 kPa sothat the resin 60 enters the gap between the mounting substrate 10 andthe ceramic substrate 30.

Next, the sealing member 50 is poured from above the light-emittingelements 40. The sealing member 50 is applied by potting from above thelight-emitting elements 40.

Thus, the light source can be easily manufactured.

The light source according to the embodiments of the present inventioncan be used for light source for lighting applications, on-vehicle lightsource, light source for mobile phones and the like.

As shown in the above, a light source, a method of manufacturing thelight source, and a method of mounting the light source are illustratedin accordance with the embodiments for carrying out the presentinvention, but the scope of the invention is not limited to the abovedescription, and should be widely understood based on the scope of claimfor patent. Further, based on the above description, it will be obviousthat various changes and modifications can be made therein withoutdeparting from the scope of the invention.

What is claimed is:
 1. A method of manufacturing a light sourcecomprising: forming a plurality of metal bumps on a mounting substrate;providing a ceramic substrate having at least one light emitting elementmounted thereon; and bonding the mounting substrate and a ceramicsubstrate to each other via the metal bumps.
 2. The method ofmanufacturing a light source according to claim 1, further comprising,after the bonding step, filling a space between the metal bumps with aresin.
 3. A method of manufacturing a light source comprising: forming aplurality of metal bumps on a mounting substrate; placing a ceramicsubstrate on the mounting substrate; bonding the mounting substrate andthe ceramic substrate to each other via the metal bumps; and mounting atleast one light-emitting element on the ceramic substrate.
 4. The methodof manufacturing a light source according to claim 3, furthercomprising, after the bonding step, filling space between the metalbumps with a resin.
 5. A method of manufacturing a light sourcecomprising: forming a plurality of metal bumps made of gold, copper, agold alloy, or a copper alloy on a ceramic substrate; placing theceramic substrate on a mounting substrate; bonding the mountingsubstrate and the ceramic substrate to each other via the metal bumps;and mounting at least one light-emitting element on the ceramicsubstrate.
 6. The method of manufacturing a light source according toclaim 5, further comprising, after the bonding step, filling a spacebetween the metal bumps with a resin.
 7. A method of manufacturing alight source comprising: forming a plurality of metal bumps made ofgold, copper, a gold alloy, or a copper alloy on a ceramic substrate onwhich at least one light-emitting element is mounted; placing theceramic substrate on a mounting substrate; and bonding the mountingsubstrate and the ceramic substrate to each other via the metal bumps.8. The method of manufacturing a light source according to claim 7,further comprising, after the bonding step, filling a space between themetal bumps with a resin.
 9. A method of mounting comprising: forming aplurality of metal bumps on a mounting substrate; and bonding themounting substrate and a ceramic substrate placed on the mountingsubstrate to each other via the metal bumps.
 10. A method of mountingcomprising: forming a plurality of metal bumps made of gold or a goldalloy at a ceramic substrate; placing the ceramic substrate on amounting substrate; and bonding the mounting substrate and the ceramicsubstrate to each other via the metal bumps.